Do exactly as RM686 suggested, it is usually the second thing I do to my Glocks after installing TruGlo sights. I put the trigger in the fired position and then use a half round jewelers file to bring the tab flush with the rest of the trigger and then sand it and the ribs with 400 grit emery and then 600 grit. The sanding takes the sharp edges off but doesn't remove a noticeable amount of material. This is a huge improvement and will not affect the operation of the safety. (which in my mind is a joke to start with).

Only thing to add is that it is easier to start by scraping the trigger safety down with a small sharp knife with the blade at right angles to the surface. The design is indeed very poor ergonomics.